Medicines ineffective: intestinal bacteria consume medicines that have been taken

How our gut affects the effectiveness of medication

Sometimes taking medication does not really improve. This can be related to certain gut microbes. Researchers have now found that medications taken are partially consumed by the microbes in our intestines or rendered ineffective.

The latest study by the internationally highly recognized Harvard University found that certain intestinal microbes can nullify the effectiveness of medication taken. The results of the study were published in the English-language journal "Science".

Gut microbiome is vital for health

Our gut is critical to the body's ability to use all kinds of nutrients that we would otherwise normally not have. The more we learn about the so-called microbiome, the clearer it becomes that our microbiome is of vital importance for our general health. However, the trillions of intestinal bacteria can sometimes have negative effects.

Bacteria can make drugs toxic

The researchers found that some intestinal bacteria can break down certain medications, such as those used to treat Parkinson's disease. This process makes the drugs ineffective or even toxic. The study could help develop special medicines that prevent intestinal attempts to consume, block, or render drugs ineffective.

Effectiveness of drugs varies from person to person

Simply taking medication is no guarantee that the medication you are taking will be effective. How well medication works depends on an almost infinite number of factors from person to person, such as taking other medications, body weight and metabolism. Any medication taken orally (in the form of a pill, capsule, or liquid) must cross the gastrointestinal tract. However, in order to achieve a goal that is outside the gastrointestinal tract, the drug must be designed to withstand the human body's attempts to digest it, the researchers explain. It is known that medicinal products must have coatings or other properties in order, for example, to withstand the acid attacks in the stomach.

Effect of microbes on a Parkinson's drug was analyzed

The increasing understanding of the trillions of bacteria in our intestines shows that these bacteria are able to break down medication. After the researchers found out how microbes affect heart failure medications, further tests were performed to determine how our gut flora could affect other medicines. The researchers tested intestinal microbial activity on a drug called L-Dopa. L-Dopa is used to treat Parkinson's, an incurable neurological disorder characterized by a lack of dopamine. The drug is said to replace part of the neurotransmitter in a patient's brain. However, previous studies have shown that only one to five percent of the drug payload actually crosses the blood-brain barrier and reaches the goal. Therefore, the dosage has to be very high and the effects are less strong than hoped. L-Dopa is now being combined with another drug for treatment that prevents the body from metabolizing dopamine. Metabolism has a lot of different effects that are not really cleared up. The effects of the study are generally very different from person to person.

Effect of antibiotics

Previous antibiotics also prevent the body from breaking down dopamine. The researchers suspect that the intestinal bacteria that are destroyed by these drugs are usually able to wipe out dopamine. They tested L-Dopa on a variety of human gut bacteria. Certain bacteria consumed L-dopa when it was added to the body for treatment. This gives the researchers the understanding on hand to develop a better defense against the important drug against the intestinal metabolism.

New drugs need to be developed

Drug development should always take into account which microbes and which molecules the drug may be susceptible to. Can microbial enzymes and profiles be used as biomarkers to predict how much of a particular drug is needed to treat a person with minimal side effects? The researchers hope that drug manufacturers can develop new molecules that prevent the microbe species from consuming L-dopa. This could produce a more effective version of the drug in the future. (as)

Author and source information

This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.


  • Discovery and inhibition of an interspecies gut bacterial pathway for Levodopa metabolism

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